Biden hints at a 2020 run

ROUGH CUT (NO REPORTER NARRATION) Former U.S. Vice President Joe Biden hinted at a 2020 presidential run on Tuesday at a cheering audience at the International Association of Fire Fighters (IAFF) in Washington, D.C.

"I appreciate the energy you showed when I got up here, save it a little longer, I may need it in a few weeks," Biden said after the crowd cheered 'run Joe run!'.

Biden then said, 'be careful what you wish for' and laughed.

Biden has a decades-long relationship with the IAFF, a labor union that represents more than 300,000 workers, and IAFF President Harold Schaitberger has urged Biden to jump into the White House race.

An early endorsement from the union would give Biden extra momentum in a crowded field of more than a dozen Democrats jockeying for the party's presidential nomination.

It could also be an exception this election cycle.

With so many labor-friendly Democratic candidates in the mix, unions expect to have increased clout.

But there will be stiff competition to get their formal backing, and endorsements may come later than in past cycles - or not at all, union leaders said in interviews.

"We aren't rushing in making a decision this time around because we believe the field is so strong and we want to give people an opportunity to answer questions," said Lee Saunders, the president of American Federation of State, County and Municipal Employees (AFSCME), which represents more than 1.6 million public employees.

Unions are a force in Democratic politics and endorsements can be a powerful force in primaries and general elections, marshalling the support of millions of union members across the country.

If labor groups hold off on endorsing, however, it could mean less organized support from their members for any specific candidate.

Those efforts often include making phone calls and knocking on doors to educate and mobilize voters.